How have scientists determined that most of the CO2 increases have come from human burning of fossil fuels, rather than natural sources?
A) Carbon isotope analysis indicates the source is fossil carbon.
B) There haven't been enough volcanic eruptions since the observed CO2 increases to account for the additional atmospheric carbon.
C) Prior to the industrial revolution, CO2 concentrations were negligible, while other greenhouses gases dominated the atmosphere.
D) Paleoclimatological reconstructions which show higher CO2 concentrations than pre-industrial times.
E) CO2 concentrations are much higher in urban areas than in rural areas, indicating fossil fuels must be the source.
A
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The cleanest burning alternative among the fossil fuels is ______________ __________
Fill in the blanks with correct word
All of the following involve the input of energy except.
A) melting. B) evaporation. C) freezing. D) sublimation.
Belgium's language boundary sharply divides the country into two regions. What are the two languages spoken in these two regions?
A) French and Walloons B) French and Flemish C) Italian and German D) Dutch and German E) Italian and Dutch
Which of the following best describes natural gas?
A) It can be converted to a liquid synthetic oil but costing many times more per barrel than conventional oil. B) It can be transported only in gas form, making the movement of natural gas over oceans impossible. C) It may help extend the oil economy by several decades. D) It cannot be used to power automobiles or public transportation.